Currently there is increasing interest in complexes of transition metals having a novel structure. Potentially such compounds could have significant use in a number of applications such as chemical processing, herbicides, pesticides and possibly medical fields.
Recently there has been significant interest in the catalyst of Brookhart et al which may activate later transition metals in a polymerization process. Such complexes are disclosed, for example, in World patent application 96/23010 jointly in the names of The University of Carolina at Chapel Hill and E.I. DuPont published Aug. 1, 1996. The Brookhart et al patent application does not teach the complexes of the present invention.
The recent paper (Chem. Comm (1998) p. 849) by the coworkers of Gibson at Imperial College UK (and BP) teach complexes having a novel structure that is dissimilar to the complexes of the present invention. It is postulated the complexes of Gibson will have utility in the polymerization of certain monomers such as alpha olefins.
There has been a great deal of work recently by both Exxon in the field of metallocene chemistry and by the Dow Chemical Company in single site constrained geometry complexes. As far as applicant has been able to determine none of the chemistry proposed by either Exxon or Dow contain a carbene atom or a constrained alkyl carbon bonded to a transition metal.
There are several patents relating to amidinato complexes of transition metals which are suitable for the polymerization of various olefins. U.S. Pat. No. 5,502,128 issued Mar. 26, 1996, assigned to the University of Massachusetts, teaches such complexes may be used to polymerize vinyl aromatic monomers; and U.S. Pat. No. 5,707,913 issued Jan. 13, 1998, assigned to BASF, teaches such compounds may be used polymerize olefins. Neither of these patents disclose complexes of the structure of the present invention.
U.S. Pat. No. 5,557,023 issued September, 1996, teaches the use of some complexes of transition metals to oligomerize lower alpha olefins such as ethylene to higher olefins such as hexene and the like. The complexes of the patent do not contain a carbene atom or substituted carbon bonded to the transition metal.
Applicant has been unable to identify any prior art disclosing the complexes of the present invention. In short the complexes of the present invention represent a novel chemistry having potential applications in many fields.